Unity is Like Dew from Heaven

At the end of Psalm 133 the authors describes the result of unity as, “the dew of Hermon, which falls on the mountains of Zion!” I don’t really have any idea what that means, but one really smart, dead guy named John Gill did. He wrote, 
the dew fell in great plenty {from the mountain}; and {it} is here compared, because it comes from God in heaven, as the dew does. {the dew from heaven}, because of its gentle nature, makes men pure, and peaceable, and gentle, and easy to be entreated; as the dew falls gently in a temperate and moderate air, not in stormy and blustering weather: and because of its cooling nature; it allays the heats and animosities in the minds of men; and because it makes the saints fruitful, and to grow and increase in good works;